An apparatus provided with a plurality of processing units such as an image forming apparatus and the like is provided with a plurality of control circuit boards carrying processors such as SOC or CPU which operates according to separate programs. Conventionally, there is an image forming apparatus which displays an error on a display device on an operation panel in a case in which there is a control circuit board that cannot start normally. However, a conventional image forming apparatus cannot display an error correctly in a case in which the CPU controlling the display device cannot start normally. For example, an apparatus which operates the display device through a control signal from the CPU of a main control section cannot display an error correctly in a case in which the CPU of the main control section cannot operate normally.